In the manufacture of large electronic systems it is common practice to have the individual subassemblies on printed circuit cards which are plugged into jacks that are wired to interconnect the cards into a functional system. The wiring that interconnects the various jacks into which the printed circuit cards are plugged into also includes some printed circuitry, but do not include the signal connections between the card jacks. Much of this latter type of wiring is done on machinery which indicates to an operator where a wire is to be placed initially and where it is to be terminated. A machine of this type is one manufactured by the Computer Numerical Control Corporation and designated Model No. 1000-SSS. This is a semi-automatic machine that is programmed to indicate to the operator where a wire is to be placed and in the case of paired wiring whether the prime wire, the dark wire, or the mate, the lighter wire, is to be placed on a particular terminal.
While performing such wiring assignment terminations, possible cross wiring may occur. This is frequently due to human error in placing for example a blue or black wire of a twisted pair of wires into the wiring gun without proper sequencing. Heretofore, there has been no way of determining if the wires were indeed terminated properly. If the wires were cross-connected, the net that the wires were in would be a broken net, and both functions of the net would be grounded, since the wiring terminals for the mating wire are grounded. In frame testing, these problems are difficult to detect and time consuming to repair.